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Missing V-8


Toranadic90

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:( I have a '91 Cadillac Seville with a 4.9. Does any one have any idea why the cylinders would start missing after about 5-10 minutes of running on the track? It does not do this while it is sitting idling. You can rev the motor and it still doesn't do it. It only seems to do this when its in gear. The motor dosen't get hot either 195-205 (manual fan). It is run at about 4500- 5000 rpm in 2nd gear. I've had good luck with these motors 4.5 and 4.9. I have had one other motor do this same thing and never could find out what it was (4.5). I ran that motor for a whole year (32 races). If you can help thanks.
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I have no experience with the 4.9, but that could be a plug wire issue or some other type of short ... does it just happen while cornering or accelerating perhaps??

Any other specifics to the behavior??

Just curious, but what kind of racing? Just heard about some 90 something caddy's running dirt track just this week.

We would love to see some pics.

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Check the coils.

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Check the coils.

I changed the wires, plugs, distibutor, messed with the timing, checked connections. Could the heads be warped? Don't know. This only happens when its being driven. I'm the same one that races on the dirt. Haven't raced this year yet, last week was the first race and the car isn't running right. I have some old pics of my old cars I have to get put on a CD to download. Can you put videos on this site? Also mt brother in law has a '94 Seville with a 4.6 Northstar and it sounds like its running out of gas going around the corners only. Down the staight it runs great. He has changed the coils,fuel pump and made sure it has enough fuel in it (almost a full tank). thanks again fir the info.

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No, I didn't disable the EGR and no it does not have traction control, although one time I welded the spider gears in the differential together. That didn't work out to well, it busted the nose piece on the transmission and broke the diff. Replaced them with spares. And yes Mr.1991sts it is fun for 5 mins boy I wish it woul be longer than that. I have never had this much trouble with a Cadillac. I guess if all else fails i'll put a carberator on it and race it. If it still runs that way I may swap the motor. Thanks for your help. if you think of any thing else please let me know. U2B

No, I didn't disable the EGR and no it does not have traction control, although one time I welded the spider gears in the differential together. That didn't work out to well, it busted the nose piece on the transmission and broke the diff. Replaced them with spares. And yes Mr.1991sts it is fun for 5 mins boy I wish it woul be longer than that. I have never had this much trouble with a Cadillac. I guess if all else fails i'll put a carberator on it and race it. If it still runs that way I may swap the motor. Thanks for your help. if you think of any thing else please let me know. I almost forgot STS, if you want to put your '91 Caddy on the track we can kick the windows out of it, put a cage in and have alot of fun. U2B

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You replaced the plugs and wires but there is the possibility that one of the new plugs or wires is defective. There is a method to disable the individual injectors through the onboard diagnostics. Search the archives or maybe someone with a 91 shop manual will post the procedure.

When the engine begins to miss, turn off each cylinder until you find the one that does not make the problem worse and then focus your efforts on the plug/wire for that cylinder. A shop can also put a scope on the engine and immediately determine the source of the misfire. Keep us posted.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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